Large motor vehicles, such as cargo vehicles, are presently built with a relatively high ground clearance. One of the major reasons for this is the need to use these vehicles on uneven surfaces. At the front of the vehicle, the ground clearance is normally on the order of about 40 to 50 cm.
The fact that a cargo vehicle normally has a relatively high ground clearance, however, poses a serious traffic safety risk. This is due to the fact that in the case of a head-on collision between a cargo vehicle and a passenger car, there is a risk that the front part of the passenger car will slide in under the front of the cargo vehicle and will thus be pinned between the road and the underside of the front of the cargo vehicle. This can cause the front of the cargo vehicle to penetrate into the passenger car with a great deal of force, which in turn can cause serious injuries to those travelling in the vehicle. In unfortunate cases, the cargo vehicle can even continue forward and run over the passenger car, which can, of course, cause even more serious injuries.
Various solutions have been devised in order to solve the above-mentioned problems. The cargo vehicle can be designed with a lowered front, i.e. a front in which the ground clearance is so low that there is no room for a passenger car to slide under the cargo vehicle and be pinned between the cargo vehicle and the road in the event of a collision. Such a solution, however, counteracts the above-mentioned desire for high ground clearance in order to facilitate driving on uneven terrain. A lowering of the ground clearance is thus not possible for many kinds of cargo vehicles.
Another solution to these problems is to provide the cargo vehicle with special underrun protection in the form of a reinforced structure, for example in the form of a horizontally arranged beam element in the front of the cargo vehicle. Using such an element, it is possible to prevent a passenger car from sliding under the front of the cargo vehicle. Additionally, such a reinforced structure can be so arranged that it becomes energy-absorbing, whereby the structure absorbs energy when strained. This further decreases the risk of serious injuries in the case of a possible collision.
A particular problem in connection with energy-absorbing underrun protections is, however, that it is difficult to direct the energy absorption in a controllable manner. Another problem results from expected legislation within the European Union, which defines threshold values for the stresses which an underrun protection must be able to withstand without exceeding a certain high degree of deformation. According to this legislation, such underrun protection must be able to withstand up to 16 tons of pressure without being deformed. In certain types of accidents, there can however be pressures of a considerably higher amplitude. There is thus a need for a device for underrun protection which can withstand higher pressures than these legislative demands.
A known underrun protection for cargo vehicles is shown in German patent document No. 4,103,782. This underrun protection comprises a shock-absorbing element which is arranged under the front bumper of a cargo vehicle. The shock-absorbing element can be arranged at a certain angle relative to the road. In the event of a collision with a passenger car, the bumper will be affected with a certain force, which will cause a link system to move the shock-absorbing element to a position which prevents the passenger car from sliding under the cargo vehicle.
Although this new design in principle provides good protection against underrunning of the passenger car, it has a drawback in that it comprises a large number of moving parts, which makes it unnecessarily complicated, and it creates a risk of degraded function. This solution additionally offers little possibility of directing the energy absorption in a controlled manner in the event of a collision.
Another known underrun protection for a vehicle is shown in Danish patent document No. 259,822. This system exhibits two essentially S-shaped attenuating elements, which are deformable, and which are arranged between a spring attachment of the vehicle and an underrun protection. In the event of a strain the attenuating elements are deformed, and thus absorb force.
The object of the present invention is thus to provide an improved underrun protection for cargo vehicles, which provides a reliable function, and which meets the demands made on energy absorption. In particular, an object of the present invention is to provide an underrun protection which provides a controlled energy absorption during stress.